Father-son filmmakers Greg and Shaun MacGillivray head to the Arctic for an Imax documentary on temperature changes and turn the spotlight on a polar bear family.

Polar bears tend to be camera shy, which caused problems for the filmmakers of the newWarner Bros./Imax adventure"To the Arctic,"opening Friday.

The 40-minute 3-D documentary examines extreme temperature changes in the Arctic, which has led to the permanent ice pack melting quickly and endangering the existence of animals such as polar bears, caribou, seals, walruses and birds that are indigenous to the region.

Narrated by Meryl Streep, "To the Arctic" is the latest movie from two-time Oscar-nominated filmmaker Greg MacGillivray ("The Living Sea," "Dolphins") and his producer son, Shaun MacGillivray ("Grand Canyon Adventure: River at Risk"). The film's editor, Stephen Judson, wrote the script.

The production lasted four years, including eight months on location in the Arctic — but for the first six trips,the filmmakers were unable to get any usable footage of polar bear mothers and cubs, the animals most closely associated with the Arctic.

"When it comes to wildlife filmmaking, you can have the best script in the world but you don't know what you are going to get until you are there," said Shaun. "We got incredible footage of caribou herds, good stories with other animals like the walrus and great aerial photography."

Then, on their last trip in 2010, the crew spent a month on a 130-foot ice breaker, the MS Havsel, in and around the seas of Svalbard, Norway. That is where they found their stars.

"We were with them for five days straight," Shaun said. "We got that incredible sense of both being emotionally connected to them, but also what it was like for a single mom polar bear to be raising two cubs in an environment that gets harder every day."

At one point, the ice floe the bears were resting on floated within 20 feet of the ice breaker. "Even then she would sniff at us, but she wasn't freaked," said Greg. "The captain of the boat ... he felt after observing her for a couple of days that 'this is the smartest bear I have ever been around. She is not expending energy to get away from us all. Bears I have seen expend energy — they jump in the water, they swim away and they walk along the ice floe to get away. But she said I am not going to expend any energy to get away from this boat. I am comfortable.'''

Extremely comfortable.

The first day they saw the trio, the mother and her cubs were sleeping and playing when suddenly, she began to dig a hole in the ice. "I said, 'Why is she doing that?' Maybe there is a seal there," said Greg.

But that wasn't the case. She actually fashioned a chair out of the hole. "She lounged back in the air and she huffed," said the director. "It was a certain kind of huff and all of a sudden, the two cubs came running over and it was time to nurse. She was on her back, vulnerable as she could be with her nose — which is more or less her early warning device — lower, not high like they want it to be. The captain was right. This is an exceptional bear. This is our story. We got to stay next to these bears as long as we possibly could. It was an exceptional experience."

There are many "Aww" moments in the film with the cubs rough-housing and playing hide and seek on the ice floe. One of the cubs loves to play with its own paw.

But there was a lot of heavy drama because the bears' primary food source, seals, are not as plentiful as they once were. So male polar bears are now devouring bear cubs for sustenance. The MacGillivrays were able to capture frantic moments when the mother bear was trying desperately to save her cubs. "Our hearts were in our throats," Shaun said, especially because their rule as filmmakers is that they can't interfere with Mother Nature.

Each time, though the mother bear was able to hold off the attack. "She was just so amazing to be able to stand up to the male polar bear and be able to communicate with her cubs to always stay in front of her," said Shaun.